Carbon dots (CDs) have attracted increasing attention as fluorescent agents for elastomer composites. Bottom-up synthesis of carbon dots (CDs) from molecular precursors would inevitably produce crude carbon dots (CCDs), i.e., a mixture of CDs, quasi CDs, polymer clusters, and molecular fluorophores. The CCDs are normally subjected to purification processes to obtain the pure CDs, while the purification procedures are time-consuming, expensive, and difficult to be scale-up. Herein, we directly used the CCDs as the fluorescent agents for silicon rubber. To achieve a good CCDs dispersion within the polymer matrix , we firstly prepared the CCDs fluid by mixing the CCDs solid with water, then the CCDs fluid was melt-mixed with the SiR (with the silica as filler) by a two-roll mill. The results revealed that small amounts of CCDs (less than 1 phr) could endow the matrix with intriguing luminescent property. Overall, this work offers a green and facile strategy to use CCDs as low-cost fluorescent agents for the SiR through melt-milling of CCDs fluid and rubber, which can be extended to a variety of other melt-processable polymer matrices (such as millable polyurethane rubber) and enables a broad range of potential applications.
Natural rubber (NR) is acknowledged to be a strategically important material, which spans multiple applications from tires to shock absorbers, generally, the antioxidant is indispensable for NR to prolong the service life and improve the long-term reliability. Recent reports demonstrated that the purified carbon dots with the capability of scavenging oxy radicals can be effective antioxidants for rubbers. However, the application of purified CDs is greatly restricted by the multiple tedious, complicated, time-consuming, and expensive post-purification processes. Herein, we first synthesize the amine-passivated crude carbon dots (CCDs) by a facile microwave-assisted pyrolysis method, and we attempt to directly use the CCDs (without any purifications) as a novel and inexpensive antioxidant for NR. To achieve a fine CCDs dispersion within NR matrix, we disperse the CCDs into the NR matrix by the liquid feeding and in-situ compatibilizing. The CCDs fluid was firstly prepared by mixing the CCDs with water, then the CCDs fluid together with the compatibilizer was melt-compounded with NR. The results showed that the well-dispersed CCDs endowed NR with the impressive antioxidative property. Overall, this work extends application scope of CCDs and provides unique inspiration to develop novel and effective antioxidants for elastomers.
Rubber is widely recognized as an important material, whose irreplaceable applications range from damping materials to tires. Generally, rubber is vulnerable to oxidative degradation , leading to a deterioration in the material's performance. Therefore, antioxidants are often added to extend the service life of rubber. In this study, crude lignin-based carbon dots (CLCDs) were prepared by a simple hydrothermal treatment of lignin with H 2 O 2 and triethylenetetramine. The thus prepared CLCDs exhibit excellent radical scavenging capability, and were incorporated into natural rubber with vinyl pyridine-styrene-butadiene terpolymer (VPR) as coupling agent. The results revealed that CLCDs could endow NR with excellent antioxidative performance. Interestingly, CLCDs even show superior antioxidant effect towards rubber compared to purified lignin-based carbon dots (PLCDs). This work provides a unique source of inspiration for the preparation of low-cost, highly effective CLCDs from plant biomass waste, most of lignin being used to produce steam and energy, with excellent antioxidant capability for rubber, which is beneficial for a green and sustainable world.
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